A novel cellular automata (CA) — two-dimensional controllable CA — is proposed in this paper.  According to characteristics of two-dimensional controllable CA,  a pseudo random generating method based on two-dimensional controllable CA with a trapezoidal structure is presented.  Simulation demonstrates that pseudo random bit sequence generator based on the two-dimensional controllable CA with a trapezoidal structure is easily implemented,  and can generate high speed bit sequence and excellent statistical properties.  This novel CA is widely used in symmetrical cryptography.